I was going to stay out of this, But established stone age musical concepts
prevail to complicate issues and screw things up.
The Key of Bb has six modes. Bb Ionian, Eb Lydian, and F Mixolydian are all
major modes. C Dorian, D Phrygian, and G Aeolian are all minor modes. These are
all "relative" majors and minors to each other because they're different
stations of Tonality that can be established within the same key of Bb. they all
would have the same exact Key signature.

All of the basic chords of Autumn Leaves are in the key of Bb. Tunes can
touch on the different modal tonal centers of a Key, establishing modal tonal
centers, and then move on to establish other tonal centers within the same key.

To call Cmin7 the Key of C minor is misleading. Cmin.7 could be the Aeolian
chord of the Key of Eb, the Phrygian chord of the Key of Ab, but here it's the
Dorian chord of the Key of Bb. In Autumn Leaves it's the Dorian chord of the
Key of Bb.

I can also say that the common key structure shared by all twelve possible
keys is so fundemental, that you can bend and worry it with leading tones and
other temporary alterations, and it will always tend to snap back into it's
original "shape".

Melody can also establish it's own tonality and modality with no chords at
all. There are a myriad of folk melodies that will bare this out.

Dave Woods http://www.jazzguitarstartingright.com



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